Prenatal smoking is the leading preventable cause of low birth weight in the US. Reduction in smoking during pregnancy could result in significant improvements in pregnancy outcomes and reducing the cost of health care. There is evidence that low-intensity pregnancy smoking cessation programs may be inadequate for women who are more addicted, and at educational and economic disadvantage. Motivational enhancement strategies have shown considerable promise in the treatment of addictive behaviors. Physiological feedback highlighting prenatal effects of smoking and benefits of cessation has been found to enhance prenatal smoking cessation counseling. An intervention that combines motivational enhancement counseling and physiological feedback may have powerful effects beyond low-intensity interventions or usual counseling.